Silencer and heat recovery system



Feb. 27, 1962 J. MAIR SILENCER AND HEAT RECOVERY SYSTEM 2 Sheets-Sheet 1 Filed June 6, 1958 Feb. 27, 1962 J, MAIR 3,022,985

SILENCER AND HEAT RECOVERY SYSTEM Filed June 6, 1958 2 Sheets-Sheet 2 United States Patent 3022985 SILENCER AND HI IAT RECOVERY SYSTEM James Mair, Chatham, N.J., assignor to Chicago Bridge & Iron Company, Chicago, 11]., a corporation of lllmols Filed June 6, 1958, Ser. No. 740,452 9 Claims. (Cl. 261-451) This invention relates to a novel combination noise silencer and heat recovery system for use in connection w th pressure vessels which are subjected to cyclical operation, such as, for example, steam autoclavesfor pressure curing of concrete products. 7

In the cyclical operation of pressure vessels of the type under consideration, relatively large amounts of 'heat in the form of hot vapors are introduced into the vessel durmg the warm-up portion of the cycle, relatively small amounts of heat in the form of vapor are introduced after the vessel has reached its operating temperature and durmg the holding portion of the cycle, and then all vapors and uncondensible gases inside the vessel are rapidly discharged from the vessel during the blowdown portion of the cycle. The blowdown portion of the cycle usually comprises an extremely small portion of the total time cycle, and heretofore it has been difiicult to recover any significant amounts of heat from the blowdown vapors becauseof the extremely short time available for accomplishing such heat recovery.

The rapid release of blowdown vapors to the atmosphere, in addition to being inefiicient because of the substantial heat loss involved, also presents troublesome noise problems which become critical when pressure vessels located in congested business or residential areas must be blown down.

My invention has general applicability to any situation wherein vapors under pressure must be released quickly from a pressure vessel. A typical and particularly advantageous application is in the steam curing of concrete products. Concrete products are usually steam cured in autoclaves, in which the operating cycle typically consists of the introduction of steam in large quantities into the charged autoclave for a period of approximately three hours, followed by a four hour holding period in which relatively small additional quantities of steam are introduced to overcome normal radiation and convection losses and to maintain the proper operating temperature and steam pressure. At the end of the holding period the autoclave is blown down within a period of approximately 15 minutes. Unless an efiective silencer is used, .the blowdown steam is discharged at such high velocities as to emit an objectionably high level of noise. Since most concrete products plants are located in developed business or residential areas so as to be close to the source of demand, it is necesary to restrict the emisison of noise to modest levels. For this reason, a silencer similar to the typical automobile engine vmother, in which baifies are provided to muffle the noise, is used in many autoclave installations. This type of silencer, however, has not proved eifectiveto reduce the noise to acceptable levels. Furthermore, in the normal installation, no attempt is made to recover the heat of the steam and the vapors discharged during the blowdown period because of the extremely large quantities which are discharged in a very short period of time.

In accordance with this invention there is provided a greatly improved combination silencer and heat recovery system for use in venting hot condensible vapors under pressure. The invention, which for convenience will be referred to as a silencer-recovery system, is described in more detail in the following paragraphs in which reference is made to the appended drawings, in which:

ice

FIGURE 1 is a schematic elevation view and flow diagram of one embodiment of the invention;

FIGURE 2 is a schematic elevation view and flow diagram of another embodiment of the invention.

Although the invention is set forth in detail in terms of its application to a concrete curing plant in which the vapor to be condensed is steam, it is not restricted there to. Thus in another application the vapor can be any other condensible vapor, and the cooling liquid any liquid of choice, as will'be apparent to those skilled in the art.

Referring to FIGURE 1, the system of the invention comprises an insulated boiler feed water storage tank 10, together with boiler feed water circulating tubes 13 and 15 and boiler feed water circulating pump 14; and a condensate surge tank 11, together with circulating condensate tubes 17 and 20, condensate circulating pump 21, and condensate overflow tube 19. The body 12 of the silencer-recovery system contains boiler feed water heater tubes 16 connected by manifolds, e.g., 16a, to the boiler feed water tube 13 and boiler feed water return tube 15. These heater tubes 16 are positioned in the lower part of body 12 so as to be submerged in the condensate which collects therein during normal operation of the system. Also located inside the body 12 is a cold condensate pipe 22 which is attached to the condensate circulation pipe 17. Attached at spaced intervals along pipe 22 are spray nozzles 23. Condensate return pipe 20 is attached to the bottom of the body 12. A control valve 18 is located in the cold condensate pipe 17.

The steam blowdown line 24 from the pressure vessel enters the body 12 at one end, at a point above the level of the condensate 28 therein. The fiow of blow-down steam through line 24 is controlled by means of valve 24a, which, if desired, can be interconnected by any suitable means, mechanical or otherwise, with valve 18 so that these valves operate in unison, opening and closing substantially simultaneously. A hot condensate pipe 25 also may be connected to the body 12, to carry ho-t condensate which forms in the pressure vessel into the body 12. A waste fluid vent 26 is provided at the other end of the body 12. The invert of this vent 26 is positioned at the level at which the condensate is desired to be maintained in the body 12.

It may be desirable on some installations to provide limited venting of the pressure vessel, particularly during the warming portion of the cycle. When such venting occurs there is necessarily a certain amount of steam and hot vapor which passes through the vents in addition to the non-condensible gases which it is desired to be vented. Under such a situation, further economy can be achieved by passing the vented gases through the condensate in the silencer-heat recovery system body and thereby condensing the steam and vapors. A vapor vent inlet for this purpose is shown in FIGURE '1 as item 27.

In operation, the boiler feed water circulation pump 14 runs continuously, circulating boiler feed water between the heater tubes 16 and the boiler feed surge tank 10. The hot condensate pipe 25 remains open at all times, thus supplying hot condensate to the body 12 in heat exchanging relation with the boiler feed water circulating within the heater tubes 16. The condensate circulation pump 21 also runs continuously pumping cooled condensate from the lower portion of the body 12 into the condensate surge tank 11 through the condensate pipe 20. As an additional optional feature, a condensate overflow pipe 19 is connected between the top of the condensate surge tank and the body 12, and remains open at all times, so that as the condensate surge tank 11 becomes full, the warmer condensate which has risen to the top overflows into pipe 19 and is returned to body 12 for additional heat recovery.

During the initial high heat input portion of the cycle,

a substantial amount of steam in the pressure vessel is condensed. This is a relatively dirty hot condensate which cannot be mixed with boiler feed water. it flows through the condensate pipe 25 into the body 12 to provide heat to the external surfaces of the boiler feed water heater tubes 16. The same process continues through the holding portion of the cycle. By the time the blowdown portion of the cycle has been reached, substantial amounts of heat have been extracted from the hot condensate water through the heater tubes 16 into the boiler feed water and thus is in the form of usable or sensible heat. The temperature of the condensate, conversely, has been reduced and the cooled condensate is pumped into the condensate surge tank 11.

At the start of the blowdown portion of the cycle, control valve 18 opens as the steam blowdown line valve 24a is opened. Thus, cool condensate stored in the condensate surge tank, as above described, flows through condensate pipe 17 into pipe 22 and out through spray nozzles 23 to form a condensing mist which condenses large quantities of steam coming into the body 12 from the blowdown pipe 24. This process of rapid condensation transfer substantial quantities of heat into the condensate at the bottom of the body 12 and also greatly reduces the volume of waste vapors and gases which must be discharged through vent 26. This reduction in volume of discharged wastes measurably decreases the noise level attributable to the blowdown operation.

The heat thus rapidly extracted from the blowdown steam by means of spraying cool condensate through such steam can then be exchanged from the condensate to the boiler feed water during the next cycle of operation, a period of some seven hours in the case of concretecuring autoclaves. The blowdown portion of the cycle may consist of from about one-tenth to about one-fiftieth of the total time for the cycle. It can be seen, therefore, that this invention makes it possible to recover blowdown steam heat which is captured by means of a spray during the short blowdown portion of the cycle and to transform such heat into usable boiler feed water heat during the succeeding cycle. Furthermore, the benefits obtained from this invention are multiplied when the silencer-recovery system is connected to a bank of two or more pressure vessels which operate in overlapping cyclic periods, because only a single silencer-recovery system body is required.

The embodiment shown in FIGURE 1 is a silencerrecovery system which can be placed below the floor of a room in which it is desired to accomplish spaceheating, thus giving added economy to the operation. Although in this embodiment the body 12 is horizontally elongated, it is not to be inferred that the invention is so limited. Any desired configuration of body can be used without departing from the principles of the invention. For example, another embodiment is shown in FIGURE 2, in which the silencer-recovery system body is a vertical cylinder with the condensate surge tank located on top. The numbering of parts is the same as in FIGURE 1, except that horizontal splash baffles 30 positioned inside the body 12 take the place of the spray nozzles 23 shown in FIGURE 1, with the cool condensate being introduced through a pipe at the top of the body. As the condensate splashes against the baflles it becomes a stream of discrete particles capable of rapidly condensing large quantities of steam passing upward through the body.

Other modifications may be made by persons skilled in the art without departing from the principles disclosed in this application. The specific details shown and described are given for purposes of illustration only, and no undue limitation of the breadth of the following claims is to be implied.

What is claimed is:

1. A combination silencer and heat recovery system for reducing noise emitted as a result of the rapid discharge of hot vapors from a pressure vessel and for recovering heat from said vapors, comprising a body portion having a hot vapor inlet and a waste fluid outlet spaced apart from said inlet; means for maintaining a pool of condensate within said body portion; first valve means for controlling the flow of said vapors through said inlet; a plurality of heat exchange tubes in said body portion positioned below the normal surface level of said pool of condensate, so that during normal operation of the system said heat exchange tubes are submerged in said pool of condensate; a cooling-liquid storage tank; means including a first pump for circulating a cooling liquid between said tubes and said storage tank; a condensate surge tank isolated from said cooling liquid storage tank; means including a second pump for withdrawing condensed vapors from said body portion into said condensate surge tank; means including second valve means for intermittently introducing condensate from said condensate surge tank into said body portion; and dispersing means within said body portion for breaking condensate so introduced into discrete particles.

2. The apparatus of claim 1 having means communicating between the top of said condensate surge tank and said body portion for recirculating condensate between said surge tank and said body portion when said surge tank is full.

3. The apparatus of claim 1 in which said second valve means is interconnected to said first valve means whereby both said valve means open and close substantially simultaneously.

4. The apparatus of claim 1 in which said dispersing means comprises a pipe equipped with a plurality of spray nozzles.

5. The apparatus of claim 1 in which said dispersing means comprises a plurality of baffle plates arranged for impingement thereon of said condensate from said condensate surge tank.

6. The apparatus of claim 1 in which said condensate surge tank is located at an elevation above any part of said body portion whereby condensate from said surge tank may flow by gravity to said dispersing means.

7. The apparatus of claim 1 in which said dispersing means is located between said fluid inlet and said fluid outlet in said body portion.

8. The apparatus of claim 1 in which said body portion includes a hot condensate inlet whereby hot liquids may be introduced into said body portion.

9. The apparatus of claim 1 which includes a vapor vent inlet in said body portion at an elevation below the normal condensate level whereby vented gases and vapors introduced through said inlet are cooled and condensed by contact with said condensate.

References Cited in the file of this patent UNITED STATES PATENTS 282,902 Keller Aug. 7, 1883 314,559 Baragwanath Mar. 31, 1885 537,325 Webster Apr. 9, 1895 1,818,483 Kensig Aug. 11, 1931 FOREIGN PATENTS 45 ,268 Germany Dec. 1, 1927 

